Frontiers in American Religion explores how certain religious dimensions of North America's settler colonial past, expressed and encoded in frontier religion, continue to affect its cultural present, especially its cultures of science and technology. The author argues that the frontier myth functions as a sacred history that explains the creation of the United States and a distinctly “American people.” As as a site of creation, the frontier, mythologically speaking, is a liminal zone in which hierarchies are dissolved and an egalitarian community made up of free and equal individuals emerges––a frontier communitas. Throughout the twentieth century and into the twenty-first, a variety of individuals, groups, and institutions engaged modern technologies to imitate the crossing of new frontiers to continually regenerate the racialized and gendered frontier communitas of the original creation. Taken together, Frontiers in American Religion offers an original religious history of expansionist ideas and practices within the modern US, showing how Frederick Jackson Turner's mythological frontier thesis animated several domains of science and technology, including California eugenics and human sterilization, NASA and the early years of space flight, psychedelics and other “countercultural technologies,” and the Internet.